Norway rats have 42 chromosomes in their diploid cells. If such a cell enters meiosis, how many chromosomes and double-helical molecules of DNA will be present in each daughter cell at the end of meiosis II?a. 21 chromosomes and 21 double-helical DNA moleculesb. 21 chromosomes and 42 double-helical DNA moleculesc. 42 chromosomes and 42 double-helical DNA moleculesd. 42 chromosomes and 84 double-helical DNA molecules

Verified step by step guidance

1. Step 1: Understand the problem. The question is asking how many chromosomes and double-helical DNA molecules will be present in each daughter cell at the end of meiosis II, given that Norway rats have 42 chromosomes in their diploid cells.
2. Step 2: Recall that meiosis is a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell. This is a process of sexual reproduction in eukaryotes.
3. Step 3: Since Norway rats have 42 chromosomes in their diploid cells, at the end of meiosis II, each daughter cell will have half of this number, which is 21 chromosomes.
4. Step 4: Recall that during meiosis, each chromosome is replicated once, and the cell is divided twice. Therefore, each chromosome consists of two identical sister chromatids, which are separated during meiosis II. So, each of the 21 chromosomes will have one double-helical DNA molecule.
5. Step 5: Therefore, the correct answer is a. 21 chromosomes and 21 double-helical DNA molecules.

Key Concepts

Meiosis

Meiosis is a specialized type of cell division that reduces the chromosome number by half, resulting in four genetically diverse daughter cells. It consists of two sequential divisions: meiosis I and meiosis II. During meiosis I, homologous chromosomes are separated, while meiosis II resembles mitosis, where sister chromatids are separated. This process is essential for sexual reproduction, producing gametes with half the original chromosome number.

Chromosome Number

In diploid organisms, chromosomes exist in pairs, with one set inherited from each parent. Norway rats have 42 chromosomes in their diploid cells, meaning they have 21 pairs. During meiosis, the diploid number is halved, resulting in haploid gametes that contain only one chromosome from each pair. Thus, after meiosis, each daughter cell will have 21 chromosomes.

Double-Helical DNA Molecules

Each chromosome consists of a single double-helical DNA molecule. During the S phase of the cell cycle, before meiosis begins, each chromosome is replicated, resulting in two sister chromatids per chromosome. However, during meiosis II, the sister chromatids are separated, leading to each daughter cell containing one double-helical DNA molecule per chromosome. Therefore, at the end of meiosis II, each daughter cell will have 21 double-helical DNA molecules.